Method and system for performing upright magnetic resonance imaging of various anatomical and physiological conditions

ABSTRACT

Vasculature or parenchyma is imaged using upright MRI techniques, on patients who may have conditions such as congestive heart failure, or otherwise be healthy. When an individual is horizontal, venous drainage is minimized, causing the vessels to remain engorged, also referred to herein as vascular congestion. Vascular congestion results in an enlarging of the vessels and surrounding tissue causing the vessels to be more visible on MRIs. The decrease in vascular visibility in upright subjects is in part, due to an increase in venous drainage. Patients suffering from coronary and/or pulmonary deficiencies (e.g. CHF) experience decreased rates and degrees of venous drainage. In one embodiment, the present invention uses upright imaging to visualize these enlarged vessels.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 15/720,747, filed Sep. 29, 2017, which is a continuation of U.S.patent application Ser. No. 14/291,265, filed May 30, 2014, nowabandoned, which is a continuation of U.S. patent application Ser. No.13/679,405, filed Nov. 16, 2012, now abandoned, which is a divisional ofU.S. patent application Ser. No. 12/832,623, filed Jul. 8, 2010, nowabandoned, which claims the benefit of U.S. Provisional PatentApplication No. 61/270,405, filed Jul. 8, 2009, all of which are herebyincorporated herein by reference.

BACKGROUND

Magnetic resonance imaging (“MRI”) offers numerous advantages over otherimaging techniques. MRI does not expose either the patient or medicalpersonnel to X-rays and offers important safety advantages. Also, MRIcan obtain images of soft tissues within the body which are not readilyvisualized using other imaging techniques. This feature makes MRIparticularly useful in analyzing the parenchymal lung tissue andpulmonary vasculature in certain patients.

Different tissues produce different signal characteristics. Tissueshaving a high density of nuclei will produce stronger signals thantissues with a low density of such nuclei. Furthermore, relatively smallgradients in the magnetic field are superimposed on the static magneticfield at various times during the process, so that magnetic resonancesignals from different portions of the patient's body differ in phaseand/or frequency. If the process is repeated numerous times usingdifferent combinations of gradients, the signals from the variousrepetitions together provide enough information to form a map of signalcharacteristics versus location within the body. Such a map can bereconstructed by conventional techniques well known in the magneticresonance imaging art, and can be displayed as a pictorial image of thetissues as known in the art.

Conventionally, MRI machines require that a patient lie in a horizontalposition and then be advanced into a tubular enclosure within asuper-conducting solenoidal magnet used to generate the static magneticfield. This method of imaging creates a unique challenge with somepatients. For example, patients with congestive heart failure, or othercardiac or pulmonary related conditions, may experience orthopnea (therespiratory resistance of the lungs increases upon transitioning fromthe seated to the supine posture). when placed in relatively supine orhorizontal positions. This makes obtaining accurate diagnostic images ofthese patients very difficult. Ferromagnetic frame magnets havinghorizontal pole axes have been developed, which alleviate the some ofthese difficulties.

Ferromagnetic frame magnets having horizontal pole axes have beendisclosed, for example, in commonly assigned U.S. Pat. No. 6,414,490,the disclosures of which are incorporated by reference herein, and U.S.Pat. No. 6,677,753, filed on Nov. 22, 2000, the disclosure of which isalso incorporated by reference herein, a magnet having poles spacedapart from one another along a horizontal axis provides a horizontallyoriented magnetic field within a patient-receiving gap between thepoles. Such a magnet can be used with a patient positioning deviceincluding elevation and tilt mechanisms to provide extraordinaryversatility in patient positioning. For example, where the patientpositioning device includes a bed or similar device for supporting thepatient in a supine or recumbent position, the bed can be tilted and/orelevated so as to image the patient in essentially any position betweena fully standing position and a fully supine or fully recumbentposition, and can be elevated or lowered so that essentially any portionof the patient's anatomy is disposed within the gap in an optimumposition for imaging. As further disclosed in the aforesaid patents, thepatient positioning device may include additional elements such as aplatform, any type of seat, or both, projecting from the bed to supportthe patient when the bed is tilted towards a standing orientation.Still, other patient supporting devices can be used in place of a bed ina system of this type. Thus, magnets of this type provide extraordinaryversatility in imaging.

FIG. 12 of the current application shows a sectional view of an MRImagnet subsystem 100. MRI magnet subsystem 100 includes a magnet havinga ferromagnetic frame 102, a flux generating means 104 as is describedin further detail below, and a patient handling system 106. Theferromagnetic frame 102 includes a first side wall 108 and a second sidewall 110. The side walls 108 and 110 extend vertically. For purposes ofclarity, FIG. 12 does not show the second side wall 110 or any of, itsassociated structures (see FIG. 5 ). The ferromagnetic frame 102 alsoincludes a top flux return structure 112 and a bottom flux returnstructure 114. The top flux return structure 112 may include two columns116 and 118. Between these two columns, a top opening 120 is defined.Similarly, the bottom flux return structure 114 may include two columns122 and 124 that together define a bottom opening 126. Thus, the sidewalls 108 and 110 and the flux return members 112 and 114 form arectilinear structure, with the top flux return structure 112constituting the top wall of the rectilinear structure, the bottom fluxreturn structure 114 constituting the bottom wall of the rectilinearstructure and the side walls 108 and 110 forming the side walls of therectilinear structure. The frame 102 of the rectilinear structuredefines a front patient opening 128 on one side of the frame 102 and asimilar back patient opening 130 on the opposite side of the frame 102.The ferromagnetic frame 102 further includes a first magnetic pole 132and a second magnetic pole 134. The first magnetic pole 132 extends fromthe first side wall 108 towards the second side wall 110 and the secondmagnetic pole 134 extends from the second side wall 110 towards thefirst side wall 108. Magnetic poles 132 and 134 are generallycylindrical and are coaxial with one another on a common horizontalpolar axis 136. Between the magnetic poles 132 and 134 is a gap 131,also referred to as the patient-receiving space, of the magnet. The gapor patient-receiving space 131 is accessed by the front patient opening128, the back patient opening 130, the top opening 120 or the bottomopening 126.

The flux generating means 104 includes a first electromagnetic coilassembly 138 which surrounds the first magnetic pole 132, and a secondelectromagnet coil assembly 140, which surrounds the second magneticpole 134. As previously noted, these electromagnetic coil assemblies 138and 140 may be either resistive or superconductive.

The patient handling system 106 is capable of three degrees or axes ofmotion. The patient handling system 106 may be termed a stand-up patienthandling system, although the patient handling system 106 is not limitedto standing position applications. The patient handling system 106includes a carriage 142 mounted on rails 144. The carriage 142 may movelinearly back and forth along the rails 144. The rails 144 typically donot block the bottom open space 126.

A generally horizontal pivot axis 146 is mounted on carriage 142. Anelevator frame 148 is mounted to the pivot axis 146. The carriage 142 isoperable to rotate the elevator frame 148 about the pivot axis 146. Apatient support 150 is mounted on the elevator frame 148. The patientsupport 150 may be moved linearly along the elevator frame 148 by anactuator 152. Thus, a patient 154 can be positioned with a total ofthree degrees of freedom, or along three axes of movement or motion.Specifically, the patient handling system 106 can move a patient 154 intwo linear directions and also rotate patient 154 around an axis. Thesolid black arrows of FIG. 12 show the three axes of movement possiblewith the patient handling system 106. Note that often the rails 108 aremounted such that portions of patient 154 may be positioned below therails through bottom open space 126.

Often, a foot rest 156 may be used in order to support a patient in astanding position. Given the wide variety of positions possible with thepatient handling system 108, many other such supports may beimplemented, such as chair seats or straps.

The patient handling system 106 incorporates one or more actuators 103and an actuation control unit 105. Actuators 103 may be conventionalelectrical, electromechanical, pneumatic, hydraulic or other devicescapable of imparting the desired motion to the elements of the patienthandling system. For example, the actuators may include elements such asconventional stepper motors or other conventional electric motors linkedto the elements of the patient handling system 106. The actuator controlunit 105 may incorporate a conventional programmable controller,microprocessor, or computer with appropriate input and outputinterfaces. As further discussed below, the actuation control unit 105is linked to a control computer and to the manual controls whichregulate the patient handling system. The actuation control unit may bemounted in proximity to the actuators 103 as, for example, on carriage142.

Of utility then are methods and systems for obtaining accuratediagnostic images of a patient's anatomy, as for example, patients withcardiac or pulmonary related maladies. These images can then be used fordiagnosis of disease.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention provides a method for evaluatingvasculature using magnetic resonance imaging comprising the steps ofplacing a patient into a magnetic resonance imaging apparatus with thepatient in an upright position, capturing magnetic resonance images ofthe patient's vasculature, and evaluating the patient's vasculaturebased on one or more of the magnetic resonance signal characteristics ofthe captured images. This particular method can be used to image anytype of vasculature, including but not limited to lung, kidney and orliver vasculature. This particular aspect of the present invention isalso useful to diagnose the presence or absence of congestive heartfailure.

The present invention is not limited only to the use of MR signalintensity to perform the methods described herein. In other anotheraspects of the present invention, any type of MR signal characteristic(e.g. signal phase, signal frequency and signal amplitude) can be usedeither independently, or in combination with one another, to aid theclinician in making clinical determinations about vasculature,parenchyma and or cardiac function.

Another aspect of the present invention provides a method for evaluatingparenchyma from magnetic resonance images, comprising placing a patientinto a magnetic resonance imaging apparatus with the patient in anupright position, capturing magnetic resonance images of the parenchymaof a selected organ or organs, and using one or more magnetic resonancesignal characteristics to evaluate the imaged parenchyma. Thisparticular aspect of the invention is also used to image lung, kidneyand liver parenchyma. This aspect of the present invention is also usedto diagnose the presence or absence congestive heart failure and alsoevaluate gravitational effects on the human lungs.

In a preferred embodiment of the present invention, a method forevaluating parenchyma vasculature from magnetic resonance images,comprising the steps of placing a patient into a magnetic resonanceimaging apparatus with the patient in an upright position, capturingmagnetic resonance images of the parenchyma of a selected organ ororgans, and using one or more magnetic resonance signal characteristicsto evaluate the imaged parenchyma. In yet another embodiment, thisparticular aspect of the present invention is used to diagnose thepresence or absence of heart failure.

In yet another preferred embodiment of the present invention a magneticresonance imaging magnet comprises a magnet frame having a pair of polefaces spaced apart from one another along a horizontal pole axis anddefining a patient-receiving space therebetween, supports holding saidframe so that said pole axis is above a floor of a structure so that apatient may enter said patient-receiving space by moving across saidfloor of said structure, a magnetic flux generator operable to providemagnetic flux in said patient-receiving space, and a rotatable patientsupport positioned in the patient receiving and rotatable between ahorizontal position and an upright, and wherein said patient issupported in an upright position and magnetic resonance images of apatient are obtained in the upright position, the images displayinginformation useful in determining vasculature or parenchyma wherein saidmagnetic resonance imaging magnet is used for upright imaging ofvasculature and parenchyma. In a further embodiment of this particularaspect of the present invention, lung vasculature and parenchyma areimaged. In yet another embodiment, those images are used to diagnose thepresence or absence of congestive heart failure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 . depicts magnetic resonance (“MR”) images of locations of the 4regions of interest (“ROIs”) in a mid-sagittal slice of the right lungused in quantitative analysis. The 4 white circles indicate where theanterior ROI (A-ROI), posterior ROI (P-ROI), superior ROI (S-ROI), andinferior ROI (I-ROI) were drawn to calculate the signal intensity oflung parenchyma. The white square outside the body depicts the regionused to estimate noise.

FIG. 2 . depicts coronal MR images of comparable anatomical locationamong 3 postures for the first participant in the study discussed in theexamples.

FIG. 3 . depicts mid-sagittal images (windowed with the same setting) ofthe right lung in the 3 postures for the second participant in the studydiscussed in the examples.

FIG. 4 . depicts variation of. Mean SNR of lung parenchyma MR signalintensity with postures.

FIG. 5 . depicts a white arrow indicating a region with some superiorlylocated blood vessels clearly visible in the supine posture and somewhatvisible in the prone posture but are absent in the upright image.

FIG. 6 . depicts axial images of the third participant in the studydescribed in the examples section in 3 postures.

FIG. 7 . depicts variation of lung parenchyma MR signal intensity alongthe anterior/posterior (“A/P”) direction with postures.

FIG. 8 . depicts the increasing lung parenchyma MR signal intensitytowards the inferior parts of the lungs when upright in the third studyparticipant.

FIG. 9 . depicts an example of no significant variation of lungparenchyma MR signal intensity in the superior/inferior (“S/I”)direction when upright in the fourth study participant.

FIG. 10 . depicts variation of lung parenchyma MR signal intensity alongthe S/I direction with postures.

FIG. 11 . depicts variation of the A/P Distance between the A-ROI andthe P-ROI with postures among the volunteers.

FIG. 12 depicts an example of an upright MRI device.

DETAILED DESCRIPTION

General

As described in greater detail in commonly assigned U.S. Pat. Nos.6,414,490 and 6,677,753, the disclosures of which are herebyincorporated by reference, an MRI system, including one capable ofupright imaging, can be provided with a patient support, such as a bedor table or any equivalent thereof, which can extend in a generallyvertical direction so that the long axis of the patient is generallyvertical. For example, the patient may be in an essentially standingposture, with his back, side or front leaning against a generallyvertical patient support. In other arrangements, the support includes aseat projecting from the table so that the seat is in a horizontal planewhen the table surface is substantially vertical. In particularlypreferred arrangements, the patient support can move relative to themagnet and may be arranged to tilt through a range of orientationsbetween a generally horizontal orientation and a generally verticalorientation.

Not many imaging modalities can handle upright imaging, largely becauseof the construction of the scanner itself. Chest radiography,scintigraphy, and MRI are among the few modalities that can image humanlungs in an upright position. Besides specific differences in the typeand quality of information offered by these modalities, chest x-ray andscintigraphy expose the patient to radiation, while MRI has theadvantage of being radiation free. This radiation free imaging modalityis beneficial for upright imaging in general, and for lung imaging inparticular.

In preferred embodiments, “Upright” as used herein generally refers toany patient position between about 0.1° and about 90°, relative to ahorizontal table, and may include positions where the patient's upperbody is at an angle greater than 90° with respect to a horizontalposition. This angle would be seen if the patient was required to leanforward. In yet other embodiments, “Upright” may refer to a patientpositioned between a recumbent and seated position. “Upright” may alsorefer to the patient can be standing or in a standing position, seatedor in a seated position. UPRIGHT® is also a registered trademark of theFonar Corporation. “Upright” as used herein is not intended to refer tothe goods identified by the registered trademark, unless indicated witha “®.”

Lung anatomy and functionality are very sensitive to body postures inboth healthy people and sick patients. The nature of illnesses affectingpulmonary and/or cardiac function affect a person's ability to lay downand maintain an adequate level of respiration, without experiencingdiscomfort and orthopnea. Clinically, this has been particularly evidentin some common life-threatening diseases such as congestive heartfailure (CHF) and acute respiratory distress syndrome (ARDS), but can beseen in any illness or condition affecting the pulmonary or circulatorysystems. For example, many CHF patients have to sit up to be able tobreathe during orthopnea.

CHF patients also may experience coughing which, can at times be bothextensive and debilitating. This presents a challenge for the clinicianperforming the imaging, as the patient's movement may prevent anaccurate image from being taken. In the recumbent position, the patientmay not be able to hold still long enough for the image to be taken, dueto orthopnea or discomfort. In the upright position, patient comfort ismaximized, while coughing episodes and accessory breathing is minimized.This makes upright imaging desirable for such patients, as they may notbe able to withstand recumbent imaging.

In accordance with an aspect of the present invention, when anindividual transitions from an essentially supine or prone position, toan essentially upright position, images of the pulmonary vasculature canbe captured at different points along the range of positions. In thisregard, the present invention is not limited to imaging in any oneposition. In preferred embodiments, the patient is positioned at a pointof comfort with the patient's upper body forming a longitudinal plane,with the plane being positioned at an angle generally between 0.1° and90° relative to a horizontal table.

Upright posture also offers an extra degree of freedom to study andmaximize gravitational effects on the lungs and pulmonary vasculature,compared to mere supine versus prone studies. Furthermore, imaging inthe upright posture is more relevant to the human condition as we spendthe majority of our lives walking, standing and sitting. This work onany subject, whether sick or healthy, and irregardless of the severityof the illness, will help clinicians to evaluate gravitational effectson the human lungs.

The posture dependency of pulmonary functions in CHF patients alsohighlights the extremely close and inseparable relationship between theheart and the lungs, and their respective physiological systems. MRI ofthe lungs can serve as a surrogate marker of cardiac functions withoutgoing through an often-invasive cardiac work-up. Coupled with uprightcapability, the multi-posture MR lung imaging described herein may offera new means of evaluating the extent of cardiac failure and itsconcomitant systemic effect on systems such as the pulmonary system. Itmay also aid in understanding how systemic physiological systems effectcardiac failure.

Because of the benefits of the present invention, patients who typicallywould experience orthopnea when subjected to traditional supine MRimaging, can now be imaged in more upright positions. One aspect of thepresent invention allows for better imaging of these types of patientsbecause the upright positioning prevents orthopnea in many types ofpatients. The diminished degree of orthopnea subsequently leads to adecrease in excessive movement, ultimately leading to a more clinicallyaccurate scan (e.g. a scan substantially void of artifact).

Parenchyma and MR Signal

Upright MR imaging of organ tissue can be used to evaluate the presenceof fluid and parenchyma, based on the MR signal strength. In particular,the parenchymal lung tissue can be imaged using MR for this purpose.This contributes to the present invention in that it demonstrates theability of diagnosing and evaluating conditions such as CHF, withouthaving to expose a patient to radiation or a posture that will inducesevere respiratory distress.

A main contributor to lung parenchyma MR signal is the blood volume inthe lungs. It is well known that venous drainage from the lungs isenhanced in the upright posture compared to the recumbent posture. Thisreduction of blood volume in the lungs could explain the drop of lungparenchyma MR signal intensity and vessel conspicuity in the uprightposture compared to the recumbent postures. Other contributing factorsinclude blood perfusion, diffusion of lung water, and lung density. Forexample, the lungs are more distended in the superior/inferior (S/I)direction when upright, hence reducing lung density and furtherdecreasing the lung parenchyma MR signal intensity which is a per unitvolume parameter.

MR signal intensity is likely to be lower, and in some cases,significantly lower, in the upright position than in the recumbentpostures. It is also expected that there should not be a significantdifference between MR intensity in the prone and supine positions. Asexpected, the overall signal to noise ratio (“SNR”) will also be lowerin the upright posture. Blood vessel conspicuity should also be lower inthe upright position compared to the recumbent positions. While notintending to be bound to a particular theory, the decreased MR intensityand decreased vessel conspicuity in the upright images is largely due todecreased blood volume in the lungs, in part due to increased venousdrainage in the upright position. Blood perfusion, diffusion of lungwater and lung density may also contribute to these results. Since thelungs have greater volume when the subject is upright, the lung tissueis less dense. The decreased density of the parenchymal tissue willgenerate a weaker MR signal.

While imaging of lung parenchyma is described in detail herein, thepresent invention is by no means limited to imaging lung parenchyma. Theupright MR imaging techniques described can be used to directly imagethe parenchyma of any organ, including but not limited to the liver,kidneys, spleen, gall bladder and intestines.

Imaging Vasculature

In one embodiment of the present invention, vasculature can be imagedusing upright MRI techniques on patients who are healthy, or who mayhave conditions such as CHF. Vasculature is defined herein according toits plain and ordinary meaning, and can include all types of bloodvessels including veins, venules, arteries, arterioles, capillaries, andtheir surrounding vascular beds.

When an individual is essentially horizontal, venous drainage isminimized, causing the vessels to remain engorged, and simultaneouslyenlarged, also referred to herein as vascular congestion. Vascularcongestion results in an enlarging of the vessels and surroundingtissue, causing the vessels to be more visible on MRIs.

In CHF patients, decreased rates and degrees of venous drainage resultin vascular congestion. Vascular congestion is prevalent and presentsnot only when the patient is recumbent, but when upright as well. Theseenlarged vessels and their surrounding tissues (e.g. parenchyma), can bevisualized using upright MRI techniques, and may be useful to evaluateand diagnose heart failure.

Heart failure (CHF) can be classified into different categories, basedon which side of the heart is affected. Right-sided heart failureaffects the right ventricle, while left-sided failure affects the leftventricle. Typically, left-sided heart failure affects the lungs andpulmonary system and results in pulmonary edema, while right-sided heartfailure generally affects systemic organs, for example but not limitedto the kidneys and liver.

In aspects of the present invention, upright MR imaging of thevasculature of organs and their surrounding tissues can be performed. Inpreferred embodiments of the present invention, upright MR imaging isused to image the lungs. Patients who have enlarged or congestedvasculature as a result of CHF are ideal candidates for the MRItechniques described herein because of the likelihood of thepresentation of vascular congestion. Any patient having vasculaturecongestion, regardless of the etiology, can be imaged using thetechniques described herein.

Another aspect of the present invention includes a method for evaluatingpulmonary vasculature from magnetic resonance images, comprising thesteps of: placing a patient into a magnetic resonance imaging apparatuswith the patient in an upright position; capturing magnetic resonanceimages of the patient's lungs; using said magnetic resonance signalintensity to evaluate the pulmonary vasculature; and evaluating thepatient's cardiac function based on presence of the fluid.

Cardiac Function

Another aspect of the present invention includes a method for evaluatingcardiac function based on the presence of lung fluid as determined frommagnetic resonance images, comprising the steps of placing a patientinto a magnetic resonance imaging apparatus with the patient in anupright position; capturing magnetic resonance images of the patient'slungs; measuring magnetic resonance signal intensity from the images ofthe patient's lung parenchyma; using the magnetic resonance signalintensity to identify the presence of fluid in the lungs; and evaluatingthe patient's cardiac function based on presence of the fluid.

As MR imaging is sensitive to the presence of fluid in tissue, anincrease in fluid (e.g., pulmonary edema) will result in an increased MRintensity in the lung parenchyma. As pulmonary edema is a common symptomof congestive heart failure, the MR values will help the clinician todetermine how much fluid is present in the lungs. Once the clinicianmakes this determination, they then correlate the presence of pulmonaryedema (from the MR image) with cardiac output.

Physiological changes occur in the lungs when the patient is moved froma recumbent to an upright position. These changes are largely evident inMR images due to variations in the presence of fluid. This isparticularly evident when fluid distribution is observed in the lungparenchyma and/or vasculature. In addition to signal intensity, bloodvessel visibility and MR signal intensity gradation can also be used toevaluate lung vasculature and cardiac function.

In another aspect of the present invention, a difference, or lack thereof between the signal characteristics in upright and recumbent readings,could indicate a presence or absence of disease, or compromised cardiacfunction. While not intending to be bound to a particular theory, thisdifference in signal characteristic may be due, in part to the fact thatCHF patients will exhibit higher signal intensity in the uprightposition, when compared to healthy patients.

Adding breath-holds such as FRC (Functional residual capacity, i.e.normal tidal expiration) and TLC (Total Lung Capacity) may add to theimaging capabilities of certain embodiments of the present invention.

In addition to the presence of fluid in the lungs, the presence of fluidin other organs such as the kidneys and liver may also indicate theonset of congestive heart failure. Furthermore, the extent of the MRsignal strength generated could indicate the extent of disease present.A stronger signal would result from more fluid being present in theorgan(s), therefore indicating a more advanced stage of heart failure.Clinician's will ultimately choose which organs and/or vasculature getimaged based on sound clinical diagnosis. The organs believed to beinvolved in a particular disease would be the organs the clinicianselects.

Additionally, comparing the MR signals of different organs may help theclinician determine whether a patient is suffering from left-sided heartfailure, right-sided heart failure, or bi-ventricular failure. Forexample, an upright MR image exhibiting a strong signal from theparenchyma of the lungs may indicate left-sided heart failure, while astrong MR signal from the parenchyma of the kidneys may indicateright-sided heart failure. A strong MR signal from both the lung andkidney parenchyma may indicate bi-ventricular heart failure. Changes inthe MR signal in the parenchyma of a given organ may indicate theprogression of disease, while weak MR signal, particularly in theupright position may indicate the absence of disease. Furthermore, MRimages of parenchyma and vasculature can be used to detect variousdiseases, such as heart failure and kidney failure.

Cardiac and pulmonary function imaging are generally conducted asseparate disciplines. Being able to correlate findings between the twodomains in the same imaging session and posture is of tremendous value.

Examples

The following example describes a study performed using upright lung MRimaging on four volunteer subjects.

Scans were performed on the UPRIGHT® MRI scanner (Fonar Corporation, NewYork) at 0.6 T. With a vertical walk-in patient space, the scanner has abed that can be rotated to any angle between the vertical and horizontalposition. As a result, the patient can be scanned standing up, sittingup, flexing, extending, and lying horizontally or in thereverse-Trendelenburg position. When combined with various patientorientations such as feet first head last, Trendelenburg and lateraldecubitus positions are also possible.

Four non-smoking healthy human volunteers participated in this study (2males/2 females, age: 22-54). A body RF transmitter coil was used for RFexcitation. A separate rigid thoracic coil (quadrature receive-only)with a homogenous illumination was centered on the lungs. The imagingparameters were selected according to clinical parameters commonly knownin the art. Those imaging parameters included the following: the MRpulse sequence used was a 2D multi-slice gradient echo FLASH sequencewith a very short time to echo (“TE”): TR=80 ms, TE=0.9 ms, flipangle=25°, receive bandwidth=625 Hz/pixel, slice thickness/gap=16 mm/2mm, field-of-view=40 cm, number of excitation=1, matrix=128×128 zippedto 256×256. Scan time was about 10 s, covering the entire lungs withmultiple slices within a single breathhold. Each volunteer was scannedin 3 postures (seated upright, recumbent supine and prone, in variableorder) and in the 3 orthogonal planes (axial, coronal, and sagittal) atend expiration (residual volume (“RV”)) to maximize lung parenchyma MRsignal. They were given about 10 minutes to settle down in each postureprior to the above scans. All images were windowed identically fordirect comparison. While the present example employed the use ofspecific imaging parameters and pulse sequence, the present invention isnot limited to these specific parameters or sequence. Any or all of theimaging parameters or pulse sequence can be altered according to soundclinical principles know in the art in order to maximize the scan.

One of the most obvious changes in going from the recumbent to theupright posture is the lung volume. It has been shown that the lung areameasured on sagittal slices correlated very well with spirometry lungvolume measurement. Hence, we measured the area of the lung in themid-sagittal slice of the right lung and regarded this proxy measure ofthe total lung volume as the RV.

To quantify the overall signal-to-noise ratio (SNR) in the lungs indifferent postures, 4 regions of interest (ROI) were drawn in theperipheral lung parenchyma in a mid-sagittal slice of the right lung asillustrated in FIG. 1 . The right lung was chosen instead of the left toavoid the crowding of the lung parenchyma from the heart and its mainvessels. Care was taken not to include any visible blood vessels in thedrawing of ROIs. The anterior ROI (A-ROI) and posterior ROI (P-ROI) werelocated respectively at the anterior and posterior area of the lunghalfway in the S/I direction. The superior ROI (S-ROI) and inferior ROI(I-ROI) were located around the apex and bottom of the lung halfway inthe A/P direction. The SNR in each ROI was calculated by dividing theaverage signal intensity in the ROI by the standard deviation of signalintensity in a region of air outside the body (the square in FIG. 1 ).Mean SNR of the lungs was then calculated by averaging the SNR of the 4ROIs.Mean SNR=[SNR(A-ROI)+SNR(P-ROI)+SNR(S-ROI)+SNR(I-ROI)]/4

It was previously reported that lung parenchyma MR signal intensityincreased towards the posterior regions of the lungs in the supineposture and reversed direction in the prone posture. This gradation oflung parenchyma MR signal intensity in the A/P direction can bequantified to a good extent in the first order approximation as a linearvariation. Hence, the A/P SNR Gradation is defined as the division ofthe difference between A-ROI and P-ROI SNR by the distance separatingthe 2 ROIs (A/P Distance in cm), and then normalized by the mean SNR ofA-ROI and P-ROI to facilitate comparison with published numbers of otherresearch groups.A/P SNR Gradation (%/cm)=[SNR(A-ROI)−SNR(P-ROI)]*100%/[A/PDistance*{SNR(A-ROI)+SNR(P-ROI)}/2]

The signal gradation in the S/I direction was similarly defined.S/I SNR Gradation (%/cm)=[SNR(S-ROI)−SNR(I-ROI)]*100%/[S/IDistance*{SNR(S-ROI)+SNR(I-ROI)}/2]

A/P SNR Gradation and S/I SNR Gradation can take on positive or negativevalues. For example, a positive A/P SNR Gradation means the A-ROI has alarger SNR than the P-ROI and so on.

To determine whether the above 4 parameters (RV, Mean SNR, A/P SNRGradation, and S/I SNR Gradation) were statistically different in the 3postures, two-tailed Student's t-test was performed with P<0.05considered to constitute a statistically significant difference.

Good image quality was obtained as exemplified by the coronal imagesshown in FIG. 2 . Blood vasculature in the chest was well visualizeddown to high order blood vessels. Signal from lung parenchyma wasvisible and above noise.

Average residual lung volume of the volunteers at end expirationincreased by about 21% on going from the supine to the upright posture,and prone RV was about 5% larger than that of supine posture but thedifferences did not reach statistical significance.

A most striking difference between upright and recumbent ¹H MR lungimaging was that the lung parenchyma MR signal intensity was greatlyreduced on going from the recumbent to the upright posture, as isself-evident in FIG. 3 . The Mean SNR across the 4 volunteers in the 3postures were plotted in FIG. 4 . The lung parenchyma MR signalintensity was highest in the supine posture (Mean SNR=9), closelyfollowed by the prone posture (Mean SNR=8), and lowest in the uprightposture (Mean SNR=6). However, they did not reach statisticallysignificant difference. The overall drop in Mean SNR was about 34% ongoing from the supine to the upright posture. As the lung volumeincrease was about 21% on going from the supine to the upright posture,it makes it unlikely that the variation of lung parenchyma MR signalintensity is due to lung volume change alone.

Another visually recognizable finding was the reduction of blood vesselconspicuity on going from the recumbent to the upright posture. FIG. 5was an illustration of this effect in one of the volunteers. Thisappeared to be a general trend among all the volunteers.

The phenomenon of higher lung parenchyma MR signal intensity in thegravitationally dependent regions of the lungs in the supine and theprone posture was also evident. When the lungs were imaged in theupright posture in this study, this A/P signal intensity gradation was,much reduced and was not as visually apparent (FIG. 6 ). Thequantitative plot of FIG. 7 showed that the A/P SNR Gradation in theupright posture was much less compared to that of the supine or proneposture and took on positive as well as negative values in differentvolunteers. On the other hand, the supine A/P SNR Gradation was alwaysnegative, indicating consistent increase of lung parenchyma MR signalintensity towards the posterior lung. Similarly, the prone A/P SNRGradation showed consistent increase of lung parenchyma MR signalintensity towards the dependent region of the lungs anteriorly. AverageA/P SNR Gradation across all 4 volunteers was 0.5%/cm for upright,−3.3%/cm for supine, and 3.3%/cm for prone posture. These were allsignificantly different from each other.

With regards to the spatial gradation of signal intensity along the S/Idirection from the recumbent to the upright posture, greater subjectvariability appeared in the S/I direction than the A/P direction. Forexample, FIG. 8 showed a volunteer with a clear increase of lungparenchyma MR signal intensity towards the inferior portions of thelungs in the upright posture while no such trend was apparent in thevolunteer of FIG. 9 . Overall, 2 volunteers showed a S/I gradation ofsignal intensity while it was not significant in the other 2 volunteers.This was reflected in the quantitative plot of the S/I SNR Gradation inFIG. 10 . On average for all volunteers, the S/I SNR Gradation was−1.9%/cm for upright, −1.1%/cm for supine, and −1.7%/cm for prone anddid not reach statistically significant difference among them. Thenegative value of S/I SNR Gradation in all 3 postures indicated that thelung parenchyma MR signal intensity tended to increase towards theinferior lungs in all 3 postures, especially when upright and prone.

With 4 volunteers, 3 postures, and 4 ROIs in a mid-sagittal slice of theright lung, there are a total of 48 ROIs. The lung parenchyma MR SNRamong these 48 ROIs spanned a large range, from 3.7 to 16.1. Thisunderscores the highly sensitive nature of lung parenchyma MR signalintensity to postures and also to variability among individuals.

It is known in the art that gravitationally dependent regions exhibit ahigher peak signal enhancement and also a faster time-to-peak than thenon-dependent regions. The study indicates: −3.3%/cm for the supinepositions and 3.3%/cm for prone positions.

In the upright posture, there is little spatial gradation of lungparenchyma MR signal intensity along the iso-gravitational A/P direction(A/P SNR Gradation=0.5%/cm versus 3.3%/cm for the recumbent postures).However, in the recumbent postures, a large gradation of lung parenchymaMR signal intensity in the iso-gravitational S/I direction was observedin two of the volunteers as one case was illustrated in FIG. 8 . Oncloser examination of the images, this result is actually amanifestation of the more complex 2D nature of spatial distribution oflung parenchyma MR signal intensity. For example, the lung parenchyma MRsignal intensity of volunteer 3 in FIG. 8 showed a diagonal pattern ofstrong signal emanating from the posterior-inferior part of the lungwhen supine and switched to the anterior-inferior part when prone. Involunteer 4 (FIG. 9 ), the diagonal pattern was also evident, though inthe opposite and a weaker fashion: a low signal region emanating fromthe anterior-inferior part of the lung when supine and switched to theposterior-inferior part when prone. This diagonal distribution of lungparenchyma MR signal intensity resulted in a large negative S/I SNRGradation in the recumbent postures in volunteer 1 and 3 and a smallpositive S/I SNR Gradation in the recumbent postures in volunteer 2 and4.

Based on the heart's anatomical orientation within the mediastinum, thespatial variation of lung parenchyma MR signal intensity is not justconfined to one orthogonal axis but also exhibits a diagonal component.On the other hand, no such diagonal trend was apparent in the uprightposture in any of the volunteers. One explanation for the presence ofdiagonal spatial variation of lung parenchyma MR signal intensity in therecumbent postures, and its absence in the upright posture, could bethat this asymmetry is being diminished by the large reduction of lungblood volume in the upright posture.

Another notable observation from FIG. 10 is that S/I SNR Gradationappears to be similar across all postures within an individual. In otherwords, the S/I SNR Gradation seems to cluster around the same value andpolarity regardless of the posture for any given individual. This makesS/I SNR Gradation more subject-dependent rather than posture-dependent,contrary to the behavior of A/P SNR Gradation.

A major distinguishing feature between the A/P and S/I direction is thatthe lungs are longer in the S/I direction than in the A/P direction. Forexample, in the volunteer population of this study, the S/I Distance wason average larger than the A/P Distance by 38.2% when upright, 26.8%when supine, and 21.2% when prone. In order to search for what the S/ISNR Gradation could be dependent on if not heavily on posture, acorrelation analysis was conducted of the S/I SNR Gradation with the 3morphometric measures of A/P Distance, S/I Distance, and RV. We found asignificant correlation of the S/I SNR Gradation with the A/P Distance(correlation coefficient=0.96, significance level=0.037) when averagedacross postures but not with the other 2 measures (S/I Distance and RV).Qualitative inspection of the A/P Distance plot (FIG. 11 ) alsocorroborated its similarity with the S/I SNR Gradation profile. This ribcage size measure along the A/P direction has a similar profile to thatof the S/I SNR Gradation of FIG. 10 . Pearson's statistical testrevealed a significant correlation between the A/P Distance and the S/ISNR Gradation when averaged across postures. Correlation analysis of theA/P SNR Gradation with the 3 morphometric measures was also performedand yielded no significant correlation relationship.

Comparison with the supine and prone posture revealed major posturalchanges on going from the recumbent to the upright posture: largereduction of lung parenchyma MR signal intensity, reduction of bloodvessel conspicuity, and changes in the spatial distribution of lungparenchyma MR signal intensity. Due to the intimate relationship ofcardiac and pulmonary functions, it is foreseeable that upright MRI mayprovide a new means of quantifying the efficiency of cardiac functionand the extent of cardiac failure.

Alternative Embodiments

As an alternative to the upright position, images could be captured onpatients in the Trendelenburg position to see if the S/I SNR Gradationwould switch to a preponderance of positive values. Further imaging ofthe pulmonary blood flow between the lungs and the atria could be usefulto evaluate and diagnose cardiac functions. For example, it may help todetermine if the subject-dependency of S/I SNR Gradation is due tocardiac function variation among volunteers.

The UPRIGHT® MRI scanner has all-posture capability, including theimportant upright posture. As a result, the UPRIGHT® MRI scanner is anideal solution for proton and hyperpolarized gas MR lung imaging withmulti-posture capability.

The present invention is not limited only to the use of MR signalintensity to perform the methods described herein. In other anotheraspects of the present invention, any type of MR signal characteristic(e.g. signal phase, signal frequency and signal amplitude) can be usedeither by itself or in combination, to aid the clinician in makingclinical determinations about vasculature, parenchyma and or cardiacfunction.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

The invention claimed is:
 1. A method for providing informationdeterminative of an amount and presence of vascular congestion in apatient using magnetic resonance signals, comprising the steps of:placing the patient into a magnetic resonance imaging apparatus capableof obtaining images in an upright, Trendelenburg, prone and supinepostural positions; obtaining magnetic resonance signals of vasculatureof the patient's organ without using hyperpolarized gas; processing themagnetic resonance signals to obtain magnetic resonance image data;processing the image data to determine one or more measures ofanterior/posterior signal gradation, superior/inferior signaldegradation and mean signal-to-noise; and determining the posturaldependence of the presence and amount of vascular congestion based onthe one or more of the determined measures of anterior/posterior signalgradation, superior/inferior signal degradation and meansignal-to-noise.
 2. The method of claim 1, wherein obtaining furthercomprises obtaining magnetic resonance signals of the patient's lungvasculature.
 3. The method of claim 1, wherein obtaining furthercomprises obtaining magnetic resonance signals of the patient's kidneyvasculature tissue.
 4. The method of claim 1, wherein obtaining furthercomprises obtaining magnetic resonance signals of the patient's livervasculature.
 5. The method of claim 1, wherein obtaining comprisesobtaining magnetic resonance signals of the patient's vasculature. 6.The method of claim 1, wherein processing includes obtaining a magneticresonance image while the patient is in the upright position thatconveys information about the presence or absence of congestive heartfailure.
 7. The method of claim 1, wherein processing includes obtaininga magnetic resonance image while the patient is in the upright positionthat conveys information about the presence or absence of congestiveheart failure.
 8. The method of claim 1, wherein using intensityinformation comprises dividing an average magnetic resonance signalintensity in a region of interest by a standard deviation of magneticresonance signal intensity in a region of air outside the patient.
 9. Amethod for providing imaging information determinative of a presence orabsence of fluid in the parenchyma in a patient based on magneticresonance signals, comprising the steps of: positioning the patient intoa magnetic resonance imaging apparatus capable of obtaining images in anupright, Trendelenburg, prone and supine postural positions; obtainingmagnetic resonance signals of the parenchyma of a selected organ ororgans without using hyperpolarized gas; processing the magneticresonance signals to obtain a magnetic resonance image data; processingthe image data to determine one or more measures of anterior/posteriorsignal gradation, superior/inferior signal degradation and meansignal-to-noise; and determining the postural dependence of the presenceor absence of fluid in the parenchyma based on one or more of thedetermined measures of anterior/posterior signal gradation,superior/inferior signal degradation and mean signal-to-noise.
 10. Themethod of claim 9, wherein obtaining comprises obtaining magneticresonance signals of kidney parenchyma.
 11. The method of claim 9,wherein obtaining comprises obtaining magnetic resonance signals ofliver parenchyma.
 12. The method of claim 9, wherein processing furtherincludes obtaining a magnetic resonance image while the patient is inthe upright position that conveys information about the presence orabsence of congestive heart failure.
 13. The method of claim 9, whereinusing intensity information comprises dividing an average magneticresonance signal intensity in a region of interest by a standarddeviation of magnetic resonance signal intensity in a region of airoutside the patient.